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S7/300 cycle time

Created by: Memoli at: 4/7/2009 12:19 PM (7 Replies)

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4/7/2009 12:19 PM	Rate (0)
Memoli Posts: 15 Rating: (0)	Hi experts, We get a new machine in a short while, and the cycle time of the S7 315 is 60mS and the memory is 85%. I do not have a good feeling about it , me is told that the cycle time must be below 20mS, wy is that?
Memoli Posts: 15 Rating: (0)
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4/7/2009 12:24 PM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 8/27/2024 Posts: 2957 Rating: (242)	Hello, I see nothing wrong with cycle time 60ms. It may be not ok if controlled process is very fast and you needfast PID controllers. If process is not time critical then 60 ms is ok. I did PLC program on S7-417 where cycle time was 110 ms. Everything is working just fine. The only reason for fast cycle time may be only fast controlled process.
	Best regards, Darius
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4/7/2009 12:45 PM	Rate (0)
Memoli Posts: 15 Rating: (0)	Hi Darius, Thans for your reply, but the process is very fast, there are a lot of telegrams over TCP-IP with a server.
Memoli Posts: 15 Rating: (0)
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4/7/2009 12:55 PM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 8/27/2024 Posts: 2957 Rating: (242)	Hi, As I understand, the program is allready written and comming with new machine preinstalled. So this new machine must work as it intended to and it do the job, then it seams that cycle time is enough. For TCP/IP telegrams is responsible communication CP and it will affect cycle time minimal.
	Best regards, Darius
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4/7/2009 6:17 PM	Rate (0)
Memoli Posts: 15 Rating: (0)	HI darius, What is your oppunion with 85% memory use already? The machine is actual a produktion line that is in communication with a server for the produktion data This part is not testet yet, because those testing is going to be on our plant. So there is a lot of traffic with the server to release the parts that are build on each station.
Memoli Posts: 15 Rating: (0)
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4/7/2009 9:48 PM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 8/27/2024 Posts: 2957 Rating: (242)	Memory usage is nothing to do with performance. You may have some problems if you will ever want to upgrade program or expand your line. That's all. Everything what you need to know about performance is cycle time. If you do not plant expanding this line in the future then it's ok. You must keep in mind that new hardware in HW config will take some memory also, but 15% free memory is ok for expanding line with other CPU. Also you can allways put bigger MMC card. Its worse if you have not much left of work memory which is not expandable in CPU 315.
	Best regards, Darius
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4/7/2009 10:04 PM	Rate (0)
Denilson Pegaia Platinum Member Joined: 9/23/2005 Last visit: 10/4/2024 Posts: 4349 Rating: (1446)	Hi, despite of the percentage, it is relevant the number of free bytes that you have. If you intend to change online a block, you need so much bytes free in work / load as the size of the changed block.
	Denilson Pegaia Siemens Industry Sector Technical Support
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4/8/2009 11:36 PM	Rate (0)
Memoli Posts: 15 Rating: (0)	Thanks to @ll
Memoli Posts: 15 Rating: (0)
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